Direct Injection Combustor for Low NOx High Hydrogen Fuels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional coal-fired power plants are inefficient and pollute the air, and high hydrogen fuels pose challenges for low NOx combustion due to flashback and high NOx emissions, especially with syngas, which requires additional diluents that increase turbine mass flow and reduce efficiency.
Innovation Solution
A backside cooled reactor allows direct injection of fuel and air into catalytic reactor flow channels for in-situ mixing, eliminating the need for fuel-air premixing and enabling greater air flow, reducing the stoichiometric flame front temperature and NOx emissions, even without catalysts for hydrogen fuels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional dry low NOx premixed combustion is used for high hydrogen fuels, then NOx emissions are reduced, but flashback occurs due to high flame speed
Solution Approach 1:
The combustion process is divided into two distinct zones: a premixed combustion zone where fuel and air are mixed and burned, and a separate diffusion flame zone where additional air is introduced. This segmentation allows the premixed zone to operate at controlled equivalence ratios below flashback limits while the diffusion zone provides stable anchoring and additional NOx reduction
Solution Approach 2:
A catalytic reactor is introduced as an intermediary device between the fuel source and the combustion chamber. The catalyst promotes low-temperature oxidation reactions that reduce the flame speed of high hydrogen fuels, preventing flashback while maintaining combustion stability and enabling operation at equivalence ratios that would otherwise be too rich for safe premixed combustion
2Object-generated harmful factors
If diffusion flame combustion is used with diluents (steam or nitrogen) to reduce NOx, then NOx emissions are reduced, but turbine mass flow increases requiring compressor air bleed-off
Solution Approach 1:
The equivalence ratio is changed to operate in a fuel-rich regime (0.6-0.8) in the premixed zone, which inherently reduces flame temperature and NOx formation without requiring external diluents. The catalytic reactor enables this parameter change by controlling flame speed and allowing stable combustion at ratios that would normally cause flashback
Solution Approach 2:
The need for external diluents (steam or nitrogen) is eliminated by taking out the NOx reduction function and achieving it through internal fuel-rich combustion combined with catalytic flame speed control. This removes the harmful diluents from the system while maintaining NOx reduction
3Object-generated harmful factors
If nitrogen is added to dilute fuel gas for NOx reduction, then NOx emissions are reduced, but compression energy increases due to additional compressing requirement
Solution Approach 1:
The fuel-rich combustion, which would normally be considered a harmful condition due to incomplete combustion, is converted into a beneficial approach. By operating at equivalence ratios of 0.6-0.8 with catalytic control, the rich mixture reduces flame temperature and NOx formation without requiring energy-intensive nitrogen compression or dilution
4Adaptability or versatility
If syngas is used in gas turbine designed for natural gas, then carbon-free hydrogen production is achieved, but turbine mass flow increases requiring reduced inlet temperature
Solution Approach 1:
The catalytic reactor performs preliminary oxidation of the syngas before it enters the turbine combustor. This pre-processing controls the flame speed and allows the turbine to handle high hydrogen content fuels without experiencing flashback or requiring reduced inlet temperatures, maintaining both adaptability and thermal efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves ultra-low NOx emissions below 2 ppm, improving efficiency and reducing turbine rotor stresses, while allowing for wider turndown and carbon-free hydrogen production, enhancing the cleanliness and efficiency of coal-fired power plants.
Implementation Method 1
direct injection of both fuel and air into the catalytic reactor flow channels with in-situ mixing of the fuel and air
Implementation Method 2
the reactor is substantially protected having backside cooled walls
Implementation Method 3
backside cooled reactor allows direct injection of fuel and air into catalytic reactor flow channels
Implementation Method 4
conditions can readily be chosen to provide reaction of the hydrogen upon contact with the injected air
Implementation Method 5
the fuel flow can be used to inject much more air than would otherwise flow through the available effective open area
Data Source
AI summary
A method for low NOx combustion, without premixing of fuel and air prior to passage to a combustor, is provided wherein a fuel is injected into a reaction zone via an eductor thereby inducing an air flow and producing a fuel-rich mixture. The fuel-rich mixture is reacted and produces partial reaction products plus heat. A portion of the heat is to transferred to a cooling air stream and the cooled partial reaction products are brought into contact with the heated cooling air stream for combustion. Increased injection of the fuel results in an increased induction of the air flow.